From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06053C10F14 for ; Tue, 15 Oct 2019 11:19:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C24FA21835 for ; Tue, 15 Oct 2019 11:19:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="RQOLs/Cw" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726917AbfJOLTT (ORCPT ); Tue, 15 Oct 2019 07:19:19 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:41226 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725812AbfJOLTS (ORCPT ); Tue, 15 Oct 2019 07:19:18 -0400 Received: by mail-wr1-f68.google.com with SMTP id p4so7478817wrm.8 for ; Tue, 15 Oct 2019 04:19:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=YLk4rgpI3ra8cq7GidJOjYQl2q+Qi2SppaV+ZdIOjAo=; b=RQOLs/Cw/FVVLCXQjdKG9FW2QdL+Uxhy87PbSkpzMeryOLc5r0B1Zt+Cn74BYNXKTg kGK+cQg4Oq6PnjkvO/MPbmPv0ZtnOZIj85r2IcwdlPm3INkZRjp8e70mIbP/I5MHsqAp qCeQ4TkAsn6cq8ptza33FmiG98/NDU/T/2N75b5TbmL9g29mtTy2CfbKQYEclFlu8kI8 vj3yfsnAmUa1e6dIZwv5pmLhSth1+xtHhCgqUG32ias4GT24miXFl43wu1YoimGai9vF NwU14tjp2iLNaMN99w0waNw6UbA1DMVy5uhFD/zwLOuaVqhI6oKxyu8yVIRH9asxQqd3 eJxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=YLk4rgpI3ra8cq7GidJOjYQl2q+Qi2SppaV+ZdIOjAo=; b=UaWxgkZ3FGg/kgThGrcutTdA2LVhYQoF3LZ4qsOYg/Rni3mELDcqQwjHre5/B5kjo6 hPNFiXukOKnwoANealqzTWcg2f2B4S/Kx6BXqr+JhfqbdGhe9YSE0aqmtL1VJ9+nPHm6 KllZcU1SEmlOJitJFN3wf2NWKQY8YEPaWreVnfA2ocF25Dx/DkcfQjmFDDh7lqT/nRx8 cNfvkVmBpmxNcP/NHGDsTwhlxDDjCrib6Qrjb67lIgYAE1YKo96QaGkWmAGVku2sM33J VxV3a34jpgjdjK5+PH2ZaGZIo2fk6fIz7oCVBV+jQq3Yj9sWEm2Lo3k2h9+fyiAOfkBr aRYg== X-Gm-Message-State: APjAAAU+x3vx6fywCW3sBPvC/dDhm/W3Ai9a/b7czcmv4GjJfZfnKmY3 zn52psXfN2lrrrvn6PskFdEy3Pw= X-Google-Smtp-Source: APXvYqwMa/xwwPSZbm221EToQd+40Gefh1qrTgqpJxkJUhUdAoJfaGj7EOfnoJ2PrjjfnaZ17sZ3ng== X-Received: by 2002:adf:f50b:: with SMTP id q11mr544218wro.310.1571138356335; Tue, 15 Oct 2019 04:19:16 -0700 (PDT) Received: from buster-jangle.bmw-carit.intra ([212.118.206.70]) by smtp.gmail.com with ESMTPSA id l9sm18487303wme.45.2019.10.15.04.19.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Oct 2019 04:19:14 -0700 (PDT) From: "Viktor Rosendahl (BMW)" To: Steven Rostedt , Ingo Molnar , linux-kernel@vger.kernel.org Cc: Joel Fernandes , "Viktor Rosendahl (BMW)" Subject: [PATCH v9 2/4] preemptirq_delay_test: Add the burst feature and a sysfs trigger Date: Tue, 15 Oct 2019 13:19:08 +0200 Message-Id: <20191015111910.4496-3-viktor.rosendahl@gmail.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191015111910.4496-1-viktor.rosendahl@gmail.com> References: <20191015111910.4496-1-viktor.rosendahl@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This burst feature enables the user to generate a burst of preempt/irqsoff latencies. This makes it possible to test whether we are able to detect latencies that systematically occur very close to each other. The maximum burst size is 10. We also create 10 identical test functions, so that we get 10 different backtraces; this is useful when we want to test whether we can detect all the latencies in a burst. Otherwise, there would be no easy way of differentiating between which latency in a burst was captured by the tracer. In addition, there is a sysfs trigger, so that it's not necessary to reload the module to repeat the test. The trigger will appear as /sys/kernel/preemptirq_delay_test/trigger in sysfs. Signed-off-by: Viktor Rosendahl (BMW) Reviewed-by: Joel Fernandes (Google) --- kernel/trace/Kconfig | 6 +- kernel/trace/preemptirq_delay_test.c | 144 +++++++++++++++++++++++---- 2 files changed, 128 insertions(+), 22 deletions(-) diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index e08527f50d2a..2a58380ea310 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -752,9 +752,9 @@ config PREEMPTIRQ_DELAY_TEST configurable delay. The module busy waits for the duration of the critical section. - For example, the following invocation forces a one-time irq-disabled - critical section for 500us: - modprobe preemptirq_delay_test test_mode=irq delay=500000 + For example, the following invocation generates a burst of three + irq-disabled critical sections for 500us: + modprobe preemptirq_delay_test test_mode=irq delay=500 burst_size=3 If unsure, say N diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c index d8765c952fab..31c0fad4cb9e 100644 --- a/kernel/trace/preemptirq_delay_test.c +++ b/kernel/trace/preemptirq_delay_test.c @@ -10,18 +10,25 @@ #include #include #include +#include #include #include #include #include +#include static ulong delay = 100; -static char test_mode[10] = "irq"; +static char test_mode[12] = "irq"; +static uint burst_size = 1; -module_param_named(delay, delay, ulong, S_IRUGO); -module_param_string(test_mode, test_mode, 10, S_IRUGO); -MODULE_PARM_DESC(delay, "Period in microseconds (100 uS default)"); -MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt or irq (default irq)"); +module_param_named(delay, delay, ulong, 0444); +module_param_string(test_mode, test_mode, 12, 0444); +module_param_named(burst_size, burst_size, uint, 0444); +MODULE_PARM_DESC(delay, "Period in microseconds (100 us default)"); +MODULE_PARM_DESC(test_mode, "Mode of the test such as preempt, irq, or alternate (default irq)"); +MODULE_PARM_DESC(burst_size, "The size of a burst (default 1)"); + +#define MIN(x, y) ((x) < (y) ? (x) : (y)) static void busy_wait(ulong time) { @@ -34,37 +41,136 @@ static void busy_wait(ulong time) } while ((end - start) < (time * 1000)); } -static int preemptirq_delay_run(void *data) +static __always_inline void irqoff_test(void) { unsigned long flags; + local_irq_save(flags); + busy_wait(delay); + local_irq_restore(flags); +} - if (!strcmp(test_mode, "irq")) { - local_irq_save(flags); - busy_wait(delay); - local_irq_restore(flags); - } else if (!strcmp(test_mode, "preempt")) { - preempt_disable(); - busy_wait(delay); - preempt_enable(); +static __always_inline void preemptoff_test(void) +{ + preempt_disable(); + busy_wait(delay); + preempt_enable(); +} + +static void execute_preemptirqtest(int idx) +{ + if (!strcmp(test_mode, "irq")) + irqoff_test(); + else if (!strcmp(test_mode, "preempt")) + preemptoff_test(); + else if (!strcmp(test_mode, "alternate")) { + if (idx % 2 == 0) + irqoff_test(); + else + preemptoff_test(); } +} + +#define DECLARE_TESTFN(POSTFIX) \ + static void preemptirqtest_##POSTFIX(int idx) \ + { \ + execute_preemptirqtest(idx); \ + } \ +/* + * We create 10 different functions, so that we can get 10 different + * backtraces. + */ +DECLARE_TESTFN(0) +DECLARE_TESTFN(1) +DECLARE_TESTFN(2) +DECLARE_TESTFN(3) +DECLARE_TESTFN(4) +DECLARE_TESTFN(5) +DECLARE_TESTFN(6) +DECLARE_TESTFN(7) +DECLARE_TESTFN(8) +DECLARE_TESTFN(9) + +static void (*testfuncs[])(int) = { + preemptirqtest_0, + preemptirqtest_1, + preemptirqtest_2, + preemptirqtest_3, + preemptirqtest_4, + preemptirqtest_5, + preemptirqtest_6, + preemptirqtest_7, + preemptirqtest_8, + preemptirqtest_9, +}; + +#define NR_TEST_FUNCS ARRAY_SIZE(testfuncs) + +static int preemptirq_delay_run(void *data) +{ + int i; + int s = MIN(burst_size, NR_TEST_FUNCS); + + for (i = 0; i < s; i++) + (testfuncs[i])(i); return 0; } -static int __init preemptirq_delay_init(void) +static struct task_struct *preemptirq_start_test(void) { char task_name[50]; - struct task_struct *test_task; snprintf(task_name, sizeof(task_name), "%s_test", test_mode); + return kthread_run(preemptirq_delay_run, NULL, task_name); +} + + +static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr, + const char *buf, size_t count) +{ + preemptirq_start_test(); + return count; +} + +static struct kobj_attribute trigger_attribute = + __ATTR(trigger, 0200, NULL, trigger_store); + +static struct attribute *attrs[] = { + &trigger_attribute.attr, + NULL, +}; + +static struct attribute_group attr_group = { + .attrs = attrs, +}; + +static struct kobject *preemptirq_delay_kobj; + +static int __init preemptirq_delay_init(void) +{ + struct task_struct *test_task; + int retval; + + test_task = preemptirq_start_test(); + retval = PTR_ERR_OR_ZERO(test_task); + if (retval != 0) + return retval; + + preemptirq_delay_kobj = kobject_create_and_add("preemptirq_delay_test", + kernel_kobj); + if (!preemptirq_delay_kobj) + return -ENOMEM; + + retval = sysfs_create_group(preemptirq_delay_kobj, &attr_group); + if (retval) + kobject_put(preemptirq_delay_kobj); - test_task = kthread_run(preemptirq_delay_run, NULL, task_name); - return PTR_ERR_OR_ZERO(test_task); + return retval; } static void __exit preemptirq_delay_exit(void) { - return; + kobject_put(preemptirq_delay_kobj); } module_init(preemptirq_delay_init) -- 2.17.1